Electrically-heated sheet



May 10, 1955 T, A KERR 2,708,234

ELECTRICALLY-HEATED SHEET Filed Aug. l', 1951 Ir-Nento; Thomas A. Kem,

bld

His Attorrwetj.

ELECYRICALLYEATED SHEET Thomas A. Kerr, Fairiieid, Conn., assigner to General Eiectric Company, a corporation of New York The present invention relates to electrically-heated fabric structures, sach as electric sheets, electric blanlets, electric heating pads, etc., wherein heating wires are positioned between plies of textile material, the plies being fastened together at spaced points to form parallel ducts in which the heating wires are positioned.

An object of the invention is to provide an improved fabric structure of the above-referred-to type which can be manufactured readily at low cost and wherein the ducts for the heating wires are so formed that the heating wires are heid in the desired spaced relation relative to each other.

For a consideration of what I believe to be novel and my invention, attention is directed to the following specication and to the claim appended thereto.

The invention is especially weii adapted for use in a heating structure comprising two plies of thin textile material, such as cotton sheeting, and it is this application of my invention which I have elected to specically illustrate and describe. it is to be understood, however, that the invention is not necessarily iimited to use with cotton sheeting.

in the drawing, Fig. l is a pian view partly broken away of an electrically-heated structure embodying the invention; Fig. 2 is a similar view showing a modified construction; Fig. 3 is a plan view illustrating initial steps utilized in carrying out the improved method; and Fig. i is a detail view of a further modication.

Referring to Fig. l, 1 and 2 indicate two plies of woven fabric, such as cotton sheeting, placed one on the other and united to each other by rows of parallel zig-zag stitching 3 to form parallel ducts 4. At points spaced from the edges of the structure, alternate rows at opposite ends of the stitching have a short section of the stitching omitted to dene passages 5 at one edge and passages 6 at the other edge. connect alternate pairs of adjacent ducts 4. The passages 5 connect alternate pairs of adjacent ducts at the right-hand end of the structure and are spaced from the edge a distance to leave a length of material 7. This is the foot end of the structure and may be used for tuclting in at the foot of a bed. Passages ti connect alternate pairs of adjacent ducts at the left-hand end of the structure and are spaced only a short distance from the edge to provide a length of material 8 from the head end of the structure. Positioned in ducts 4 and passages 5 and 6 are electric wires 9 for heating the structure. The wires may be threaded through the ducts and passages by the use of suitable threading tools, the passages 5 and 6 being of sufficient length to permit readily the threading operations. To prevent the stitching from raveling where it terminates adjacent to passages 5 and 6, there are provided tack bars t, these being short bars of stitching extending transversely of the stitching 3.

The terminals of the wiring is shown at 15. At may comprise a suitable molded plug structure 16 of known type attached to the fabric structure. It is located at Passages 5 and t5 States arent Office Patented May i0, P3155 the foot of the fabric structure preferably on its longitudinal center line. The plug structure may be attached to the fabric structure by inserting the body of the plug through a buttonhole in one fabric layer and then sewing a canvas strain patch i7 over it, the sewing extending through both layers of the fabric.

In the present instance the wiring is shown as extending to the side edges of the fabric structure but if desired the wiring may be omitted from one or more of the ducts 4 at the side edges to provide Unwired portions for tucking in. The ends and side edges of the structure may be finished by suitable hemming as shown or in other desired manner.

The provision of zig-zag stitching is one important feature of the invention in that the points 11 of the Zigs and the zags cooperate to position the wires generally along the centers of the ducts, thus eftecting a substantialiy equal spacing apart of the rows of wires. in other words, the zig-Zag stitching serves to space apart adjacent ducts by an effective width equal to the distance between straight lines drawn aiong opposite sides of a row of stitches through the points of its stitches. The points of adjacent rows are spaced apart suicientiy to provide a free passage of suitable width for the wires.

in Fig. 2 is shown a form of invention wherein passages Su and (uz corresponding to passages 5 and 6 of Fig. l are formed by terminating alternate rows of zigzag stitching at opposite edges of the structure short of such edges, termination at one edge hein(y nearer to the edge than at the other to deiine the head end and foot end of the structure. Otherwise, the structure of Fig. 2 may be similar to that of Fig. i, and corresponding reference numerals with the exponent a added have been used to designate corresponding parts.

In Fig. 4 is shown a modied form of stitching wherein the rows of stitching 3a, instead of having a symetrical pattern as in Figs. i and 2, have an opposite sewing pattern so that the points 3b of adjacent rows Iare directly opposed to each other. Otherwise, the structure of Fig. 4 may be the same as that of Figs. l and 2.

The structures of Figs. l, 2 and 3 are preferably made in accordance with the following method. Plies l and Z of the material are placed one over the other and are sewn together by continuons stitching. This stitching may be performed by the use of a suitable quilting machine having drive cams of a shape to provide the zigzag stitching. With such a machine, all the rows of stitching may be formed simultaneously with one passage of the material through the machine. Material for one structure or for a desired number of structures may be sewn. If material for a number of structures has been sewn, then it may be cut as indicated at 12 into the desired lengths for the structure to be made. Either before or after the material has been cut to length, the rows of stitching may be tacked at 1d by the use of a suitable taclcing machine. The tacking should be located to define the passages 5 and 6. After the tacking operation, in the case of Fig. l construction, the stitching between the tacks is removed; while in the case of Fig. 2 construction, the stitching between the edges of the structure and the tacking is removed. The stitching may be of a chain-stitch type which is readily unraveed. After the stitching has been removed, the heating wires may be threaded through the ducts 4 and passages S and 6 by the use of suitable threading tools.

What I claim as new and desire to secure by Letters Patent of the United States is:

An electrically-heated fabric structure comprising two plies of sheet material positioned one over the other, rows of continuous pointed zig-zag stitches extending References Cited in the tile of this patent UNITED STATES PATENTS 751,353 Singer Feb. 2, 1904 4 Grapp Feb. 26, Stanton Apr. 26, Longoria May 16, Steer et al. Mar. 17, Randolph July 20, Wolfe et al. lune 4, Moberg June 11, Newell lan. 15, Moberg Dec. 16, Johnson et al. Aug. 8,

FOREIGN PATENTS Great Britain Mar. 30.

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